1. Technical Field
The present invention relates generally to improved rotor designs for helicopters and, more particularly, to an improved coaxial rotor system for helicopters which includes an upper rotor system having a plurality of upper rotor blades which are mounted on and extend outwards from a central rotor shaft, a lower rotor system having a plurality of lower rotor blades extending outwards from and connected to the central rotor shaft and rotating in a direction opposite the upper rotor system, the upper rotor system spaced an axial distance from the lower rotor system, and a circumferential rotor blade support ring which extends around the upper and lower rotor systems and engages the outer ends of each of the upper and lower rotor blades in generally parallel travel planes thereby preventing engagement of the upper rotor system with the lower rotor system during operation of the helicopter.
2. Description of the Prior Art
There are many different types of helicopters which are currently in use, including single rotor helicopters, dual rotor helicopters, transverse rotor helicopters, and several other related helicopter-type rotor-based flying aircraft. However, among the different types of helicopters currently being used, it has been found that those with dual rotors are among the most versatile, due to their increased lifting capacity from the increased air flow resulting from the two rotors being used on the aircraft. Primarily, there are three common configurations of dual rotor helicopters which utilize the contra-rotating effect to benefit the rotor craft, the first being a twin rotor design which includes two rotors mounted on the aircraft, one mounted behind the other, the second being intermeshing rotors which are mounted close to each other with the rotor blades intermeshing over the top of the aircraft, and finally a coaxial rotor design which includes two rotors mounted one above the other on the same rotational axis. It has further been found that the coaxial rotor system is generally more cost-effective, as the size of the helicopter does not have to be expanded to accommodate the position of the two rotors as they are positioned one atop another. A further benefit of the coaxial rotor design is that, in forward flight, the lift provided by the advancing ends of each rotor compensates for the retreating half of the other, eliminating one of the key effects of dissymmetry of lift, namely retreating blade stall.
Unfortunately, however, coaxial rotors have several disadvantages which must be addressed in order to permit the coaxial rotor system to function properly. For example, there is an increased mechanical complexity of the rotor system due to the required linkages and swash plates for a dual coaxial rotor system. Furthermore, because each rotor system needs to be turned in an opposite direction, the central rotor shaft or mast itself is far more complex, and provisions for making pitch changes to the upper rotor system must pass through the lower rotor system. The most significant and potentially deadly problem encountered with coaxial rotor systems, however, is that during extreme aerobatic maneuvers of the helicopter, such as those encountered during combat or the like, the upper rotor system may accidentally contact the lower rotor system during operation thereof, which results in the contacting blades disintegrating due to the high rate of speed at which the upper and lower rotor systems are rotating, and this disintegration of the rotor blades results in rapid disintegration of the remaining elements of the rotor system due to the unbalanced nature of the upper and lower rotor systems, and the entire rotor structure quickly becomes unstable and self-destructs. This, of course, results in the helicopter falling from the sky and further results in the almost certain death of the pilot and crew of the helicopter. There is therefore a need for a system or device which will generally prevent accidental intermeshing of the upper and lower rotor systems.
There are several examples shown in the prior art which attempt to address and solve this problem with coaxial rotor systems, including such Patents as Scott, U.S. Pat. No. 7,210,651 issued May 1, 2007. Scott discloses a dual coaxial rotor system which includes an upper and lower rotor system with reduced axial rotor separation distance along a common axis by way of rotor tip position sensing and rotor position control to avoid tip contact. In fact, all of the prior art devices currently known follow a similar method of attempting to address and correct the problem of rotor tip contact between upper and lower rotor systems, but, of course, in extreme conditions, these systems can fail resulting in destruction of the upper and lower rotor systems. There is therefore a need for a structural physical system which will accomplish the purpose of separating the upper and lower rotor systems while simultaneously permitting and enhancing operation of the coaxial rotor system.
Therefore, an object of the present invention is to provide an improved coaxial rotor assembly for a helicopter.
Another object of the present invention is to provide an improved coaxial rotor system for a helicopter which includes upper and lower rotor systems and a circumferential rotor blade-engaging ring which extends around the upper and lower rotor systems and movably engages and secures the outer ends of the rotor blade of each of the upper and lower rotor systems such that the distance between the upper and lower rotor systems remains generally constant due to the mechanical connections of the upper and lower rotor blades to the circumferential ring thereby substantially eliminating all possibility of physical interaction between the upper and lower rotor systems.
Another object of the present invention is to provide an improved coaxial rotor system for a helicopter which is extremely strong yet light in weight so that the substantial benefits of use of the circumferential ring of the present invention are not literally outweighed by the added weight included in the system by use of the circumferential ring.
Finally, an object of the present invention is to provide an improved coaxial rotor assembly for a helicopter which is relatively simple in design, economical to manufacture, and is safe, efficient and effective in use.